Polyalkylene carbonate is noncrystalline transparent resin, and unlike aromatic polycarbonate that is engineering plastic of a similar type, it exhibits biodegradability and can be thermally decomposed at low temperature, and is completely decomposed into water and carbon dioxide without carbon residue.
However, although polyalkylene carbonate has excellent transparency, tensile strength, elasticity, oxygen barrier property and the like, if processed in the form of a pellet or a film, it may not be easy to handle due to blocking, and dimension stability may be lowered.
Thus, there has been an attempt to use in combination with other kinds of resin that can improve the properties of polyalkylene carbonate, for example, biodegradable polylactide, and the like. Since polylactide (or polylactic acid) resin is based on biomass unlike the existing crude oil-based resin, it can be utilized as renewable resource, discharges less global warming gas CO2 compared to the existing resin when produced, and is biodegraded by water and microorganism when landfilled, and thus, is environment-friendly, and has appropriate mechanical strength equivalent to the existing crude oil-based resin.
The polylactide has been mainly used for a disposable packaging/container, coating, foam, a film/sheet and fiber, and recently, there are active efforts to combine polylactide with the existing resin such as ABS, or polypropylene and the like to reinforce the physical properties, for semipermanent use such as exterior material for a mobile phone or interior material for an automobile and the like. However, the application range is limited as yet, due to the weak points of the properties of polylactide itself such as being self biodegradable by catalyst used for preparation, moisture in the air, and the like.
A resin composition comprising polyalkylene carbonate and polylactide has limitations in that as the content of polylactide increases, unique properties of polyalkylene carbonate is rapidly degraded, thus Significantly exhibiting property offsetting, and property improvement effect is not sufficient.
For example, JP-H07-109413A suggests a blend of polylactide and aromatic polycarbonate resin. However, there are problems in that simple melt-mixing of polylactide and aromatic polycarbonate cannot achieve uniform compatibilization because of large melt viscosity difference, and that it is difficult to achieve stable pelletization because, for example, molten resin is discharged with pulsation from the nozzle of kneading extruder. And, since it has non-pearly luster, if directly mixed with a coloring agent to color, haze may be marked, and coloring may be difficult, and thus, the use is limited.
In case a sheet is prepared only from polyethylene carbonate resin and processed into an inflatable product, fusion may seriously occur between sheets, thus significantly degrading workability and product storage. In case polylactide is added to polyethylene carbonate, although sheet fusion may be improved to some degree, transparency may be degraded. Therefore, there is a demand for a resin composition that does not have fusion problem and has excellent workability and product storage, which are required for inflatable products, and can prepare product with high transparency.